Fifteen years experience with finger arterial pressure monitoring : Assessment of the technology

We review the Finapres technology, embodied in several TNO-prototypes and in the Ohmeda 2300 and 2300e Finapres NIBP. Finapres is an acronym for FINger Arterial PRESsure, the device delivers a continuous finger arterial pressure waveform. Many papers report on the accuracy of the device in comparison with intra-arterial or with noninvasive but intermittent blood pressure measurements. We compiled the results of 43 such papers and found systolic, diastolic and mean accuracies, in this order, ranging from -48 to 30 mmHg, from -20 to 18 mmHg, and from -13 to 25 mmHg. Weighted for the number of subjects included pooled accuracies were -0.8 (SD 11.9), -1.6 (8.3) and -1.6 (7.6) mmHg respectively. Subdividing the pooled group according to criteria such as reference blood pressure, place of application, and prototype or commercial device we found no significant differences in mean differences or SD. Measurement at the finger allows uninterrupted recordings of long duration. The transmission of the pressure pulse along the arm arteries, however, causes distortion of the pulse waveform and depression of the mean blood pressure level. These effects can be reduced by appropriate filtering, and upper arm 'return-to-flow' calibration to bring accuracy and precision within AAMI limits. For the assessment of beat-to-beat changes in blood pressure and assessment of blood pressure variability Finapres proved a reliable alternative for invasive measurements when mean and diastolic pressures are concerned. Differences in systolic pressure are larger and reach statistical significance but are not of clinical relevance. Finger arteries are affected by contraction and dilatation in relation to psychological and physical (heat, cold, blood loss, orthostasis) stress. Effects of these phenomena are reduced by the built-in Physiocal algorithm. However, full smooth muscle contraction should be avoided in the awake patient by comforting the patient, and coveting the hand. Arterial state can be monitored by observing the behaviour of the Physiocal algorithm. We conclude that Finapres accuracy and precision usually suffice for reliable tracking of changes in blood pressure. Diagnostic accuracy may be achieved with future application of corrective measures

Finger arterial versus intrabrachial pressure and continuous cardiac output during head-up tilt testing in healthy subjects

1. The aims of this study were to determine the clinical feasibility of continuous, non-invasive Finapres recordings as a replacement for intrabrachial pressure during a 30 min head-up tilt, and the reliability of continuous cardiac output computation by pulse contour analysis from the finger arterial versus the brachial waveform. 2. In eight healthy subjects a 30 min 70° passive head-up tilt was performed. Finger arterial (FINAP) and intrabrachial (IAP) pressures were measured simultaneously. Beat-to-beat changes in stroke volume were computed using a pulse contour algorithm. 3. Accuracy (the group-averaged FINAP-IAP difference) and precision (the SD of the difference) of Finapres measurements were 4 and 9 mmHg for systolic blood pressure, -5 and 9 mmHg for mean blood pressure and -5 and 9 mmHg for diastolic blood pressure. 4. The time course of the FINAP-IAP differences during head-up tilt showed a linear trend (P 0.05). This difference did not change at low blood pressure levels (0.5 ± 6%). 5. The qualitative performance of the Finapres allows it to be used in the clinical setting as a monitor of sudden changes in blood pressure induced by a 30 min head-up tilt. Relative changes in stroke volume, as obtained by pulse contour analysis of the finger arterial waveform, closely follow intrabrachial values during long-duration head-up tilt and associated arterial hypotension